1. Field of the Invention
The present invention relates to a method of grinding a shoulder portion adjacent to a cylindrical portion of a workpiece by a grinding wheel whose edge surface is smaller in width than the shoulder portion of the workpiece.
2. Description of the Prior Art
In a conventional method of grinding a shoulder portion adjacent and perpendicular to a cylindrical portion of a workpiece by a grinding wheel whose edge surface is smaller in width than the shoulder portion, as shown in FIG. 1, a grinding wheel G is first moved inwardly toward the axis Ow of rotation of a workpiece W along a path 10 extending at an acute angle to the axis Ow of the workpiece W to grind a radially outer portion of the shoulder portion Wb of the workpiece W by the edge surface Gb of the grinding wheel G, and the workpiece W is then moved axially to separate the shoulder portion Wb thereof from the edge surface Gb of the grinding wheel G through a predetermined distance. These steps are repeated to grind the shoulder portion Wb from the radially outer portion to the radially inner portion. According to this method, each time the grinding wheel G is moved along the path 10 against the shoulder portion Wb, only the edge surface Gb around the intersection P between the edge surface Gb and the face surface Ga is applied with a grinding resistance. Accordingly, only the edge surface Gb around the intersection P is worn out and made dull during its repeated use, so that it is difficult to accurately grind the shoulder portion Wb, particularly the corner portion R between the shoulder portion Wb and the cylindrical portion Wa.
In particular, when the grinding wheel is made of expensive cubic boron nitride and the like, the width of the edge surface Gb is made relatively small in order to increase cost efficiency of the grinding wheel. Accordingly, it is unavoidable for the grinding wheel to be partially worn out and made dull around the intersection between the edge surface and the face surface, which thus results in decreasing the grinding accuracy.